EXPLANATION OF THE TABLES OF SAFE LOADS IN 



POUNDS, UNIFORMLY DISTRIBUTED FOR 



RECTANGULAR WOODEN BEAMS ONE 



INCH THICK, ON FOLLOWING PAGES. 



(From Pocket book of the Cambria Steel Co.) 



General. 



For convenience in use, three of these tables have been 

 prepared, from which the safe loads of the various species 

 can be obtained, either directly or by proportion as stated 

 in the footnotes. 



The values given in the tables are the safe loads in 

 pounds uniformly distributed, including the weight of the 

 beam itself, for rectangular beams 1 in. thick for spans 

 from 4 to 40 ft. and for depths from 4 to 24 in. The safe 

 load for a beam of any thickness may be found by multi- 

 plying the values given in the tables by the thickness of 

 the beam in inches. 



The last column of eacn of the three Tables of Safe 

 Loads for Rectangular Wooden Beams gives a coefficient 

 of deflection, by means of which the deflection for any 

 beam may be obtained, corresponding to the given span 

 and safe load, by dividing the coefficient by the depth of 

 the beam in inches, which will give approximately the 

 deflection in inches under the given conditions. 



In each table the deflection coefficient is given for only 

 one species of wood, as shown, but the deflections for 

 other species may be obtained from these by proportion as 

 explained hereafter. 



For the reason that wood has no well-defined limit or 

 modulus of elasticity the deflections obtained by the use 

 of the coefficients are only approximate and will vary, 

 according to the moisture content of the wood and the 

 character of the loading. The deflections thus obtained 

 are, therefore, useful only as a general indication of the 

 amount of bending to be expected under the given condi- 

 tions and are not exact as in the case of materials like 

 steel, which has a well-defined limit and modulus of 

 elasticity.* 



*Nofe. "A series of tests, undertaken at the College of 

 Forestry at Cornell University, seems to demonstrate ihat, 

 ;:t I'-ast in coniferous wood, a definite elastic limit for any 

 particu.ar pit-re can be easily shown, and, that it coin- 

 cides with the theoretically calculated elastic limit upon 

 ses of compression tests and their application, ac- 

 fcording to Neely's formula." 



